1. Field of the Invention
The invention relates generally to a storage system. More specifically, the present invention relates to a multi-host management server for efficiently updating path information in a storage system in which a plurality of paths is set between a plurality of hosts and a storage apparatus(es).
2. Description of Related Art
In companies or similar environments, a storage system is constructed by connecting a plurality of storage apparatuses to a host(s) using paths via a SAN (Storage Area Network) in order to store and manage a large amount of data. Typically, not a single path but multiple paths are set between the host(s) and the storage apparatuses, which is generally referred to as “multi-path.”
Each host operates software for managing the multi-path to realize functions such as path configuration detection, path failure detection and path switching (hereinafter referred to as multi-path management software).
For a storage system having a management computer connected to hosts and storage apparatuses via a SAN, a technique for managing the multi-path has been disclosed, where when receiving a report about a path failure from a host system or a storage apparatus, the management computer commands the relevant host or storage apparatus to set a new path definition (see JP2007-72571 A).
In a large-scale system environment, a multi-host management server is provided for collectively managing and monitoring multiple paths set to each host in order to check if each host is operating normally. The multi-host management server stores path information for each host. In order to keep the path information stored in the multi-host management server up to date, a user manually operates the multi-host management server to issue a query to each host and update the relevant path information. The processing—the multi-host management server updating path information stored in the multi-host management server based on path information obtained from each host—is generally called “host refresh.”
In the above arrangement, each host monitors the statuses of paths set to the host itself. When a host detects path failure, this host reports failure information about the failure to the multi-host management server. However, a user cannot obtain up-to-date path information unless the user manually executes a host refresh. More specifically, although the user can recognize the path failure by receiving the failure information, the user cannot recognize which path the failure has occurred on without acquiring the up-to-date path information.
As described above, in the related art, the user has to manually execute a host refresh after the multi-host management server receives failure information from the relevant host, which is troublesome for the user. Accordingly, the multi-host management server is preferably set up so that it can automatically perform the host refresh.
However, if the multi-host management server executes a host refresh every time it receives failure information and as many times as the number of pieces of received failure information, unnecessary transfers of path information will occur. In particular, there is a kind of failure in which the path status is instantaneously switched between normal status and failure status (hereinafter referred to as instantaneous path interruption), and this type of failure can occur several number of times in a short time period, so executing a host refresh every time a failure occurs will result in a large load on the network.
If the failure information contains many pieces of path information, the multi-host management server can update the path information stored in the multi-host management server only by referring to the failure information. However, the increase in an amount of failure information data will increase the load on the network, so the amount of failure information data is not something that can be indiscriminately increased.
In light of these circumstances, there has been demand for a storage system capable of performing the host refresh automatically and without resulting in a large load on a network.